Electrical counter circuit



Feb- 6, 1951 W. D. HoUGHToN ELECTRICAL COUNTER CIRCUIT Filed July 27,1945 H-ff fr@ JTIHHHHHHHHHI z' .Ze

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UNITED STATES PATENT OFFICE ELECTRICAL COUNTER CIRCUIT William D.Houghton, Port Jefferson, N. Y., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application July 27, 1945, Serial No.607,296

of a frequency which is lower than but a function of a higher frequencyinput wave.

The counter circuit of the invention has numerous applications inelectrical circuits. By way of illustration, the invention may be usedin a pulse type multiplex communication system for producing a step wavevoltage and also to produce an output pulse which has a submultiplefrequency relation to an input wave; or the counter of the invention maybe used as a frequency divider of applied input waves whether theseapplied input waves are of square wave or triangular wave character.When used in a pulse type multiplex system, the different steps rorrisers in the step wave voltage may control different channel selectorcircuits. l

A more detailed description of the invention follows, in conjunctionwith a drawing, wherein:

Fig. 1 illustrates one application of the counter circuit of theinvention; and

Figs. 2a, 2b and 2c are voltage wave forms ocv curring at differentpoints of the counter circuit, given to more clearly explain theoperation of the invention.

The counter of the invention is appropriately labeled in Fig. 1 asincluding the apparatus between two vertical dash lines, and includes adouble diode A, three triode vacuum tubes V3, V4 and V5, and associatedcircuit elements, Tube V5 together with transformer T2 forms a trippingoscillator. The three vacuum tubes V3, V4 and V 5 are normallynon-conductive; that is, they are biased to the anode current cut-olfcondition. The cathodes of tubes V3 and V4 are respectively connected tothe positive terminal +B of a source 6 Claims. (Cl. Z50-27) of directcurrent potential through individual rewill be understood that, ifdesired, two separate diode tubes can be used instead of a single doublediode tube. The cathode of section DI is directly connected to the anodeof D2 and both of these electrodes are connected to a condenser C3through lead lll. The anode of diode section DI is grounded, while thecathode of diode section D2 is connected to condenser C@ across whichthe step wave voltage is developed. Condenser C3 is appreciably smallerin size than condenser C4 and these condensers may have a relation, forex-y ample, of

depending upon the number of steps or risers desired in the output stepwave voltage.

The cathode of diode D2 is also connected to the grid of triode vacuumtube V4 via lead i i as a result of which tube V4 will conduct when thevoltage built up on condenser C6 equals or exceeds the cut-off potentialvalue of tube Vt.

It should be noted that the cathodes of tubes V3 and V5 are connectedtogether by means of lead l2 and have a common cathode resistor R4.

-The grid of tube V3 is connected via lead I3 to the secondary windingof transformer T2, as aresult of which the tube V3 receives a pulse fromthe tripping oscillator when it fires, of such magnitude as to overcomethe cut-off bias on tube V3 and cause this tube to conduct. When tube V3conducts, it forms a low impedance path across condenser C4 to enablethis condenser to discharge through the space path of this tube.

There are two outputs obtainable from the counter circuit of theinvention. One output is taken from lead I6 and comprises a step wavevoltage having a desired number of steps or risers. The other output istaken from lead il' and comprises a pulse whose frequency is a sub-ymultiple of the applied input waves. The appearance of thesetwo outputsis shown in Figs. 2b and 2c. Fig. 2b shows the step Wave voltage takenfrom lead It. Fig. 2c shows the pulse voltage taken from lead Il. Fig.2a shows the pulse input to condenser C3 of the counter circuit. Thepositions of Figs. 2a, 2b and 2c above one another fairly accuratelyrepresent the timing relations of these Wave forms.

In order to supply recurring input waves to the counter, there isprovided a pulse oscillator which is appropriately labeled in thedrawing. This oscillator is a conventional blocking oscillator whichgenerates pulses. By way of example only and for the purpose of thisdescription, let it be assumed that these pulses are each about 1 psec.(microsecond) long at a 90 kc. rate. Obviously, the invention is notlimited to this particular pulse oscillator or this pulse frequency orthis particular pulse duration and the pulse oscillator can have adifferent frequency and a different pulse duration. Its frequency ofoperation is determined by the values of condenser Cl and resistor Rl.This pulse oscillator includes a pentode vacuum tube Vi and a threewinding, tightly coupled transformer Ti. The three series connectedresistors Rill, R2 and R9 comprise a bleeder circuit between thepositive terminal +B of the direct current potential source and ground.The screen grid of oscillator tube Vl is connected to resistor R2 bymeans of a tap, as shown. Output from the pulse oscillator is fed fromone of the windings of transformer Tl to condenser C3 in the countercircuit.

In the particular system shown in the drawing, which was satisfactorilytried out in practice in a pulse type multiplex communication system,the 90 kc. pulse oscillator was synchronized by a constant source of 90kc. frequency oscillations. This is accomplished by means of lead l5connecting the anode of the pulse oscillator to a crystal oscillator,not shown, which produces pulses of current at a 90 kc. rate. Inpractice, the values of Ri and CI of the 90 kc. pulse oscillator are sochosen that the frequency of this pulse oscillator is slightly lowerthan the synchronizing voltage applied to lead i5 by the crystaloscillator.

An explanation of the operation of the counter circuit of the inventionwill now be given. Let it be assumed, for example, that it is desired toobtain from the counter an output pulse from lead l1 which is one-ninth(/g) the frequency of the 90 kc. pulse oscillator, and also to obtain astep wave from output lead l which has nine steps or risers. These ninesteps or risers may be used to control eight channels in a multiplexsystem while the ninth interval may be used for synchronizing purposes.Obviously, the counter of the invention may be employed wherever thereis need for either one or both of these output waves. Let it also beassumed that the ratio of the values of condensers C3 and Cd is l to 20.

On the positive rising edge (leading or starting edge, for example) ofthe pulse applied by the 90 kc. pulse oscillator to condenser C3 in thecounter circuit, diode Dl will not conduct, though diode D2 willconduct, as a result of which the circuit will look as though the twocondensers C3 and Cd are in series relative to ground. Hence,one-twentieth of the total input voltage appears across condenser C/i,producing an incremental increase in the voltage on condenser C4. Thisincremental increase on condenser C4 is equivalent to a step or risewhose amplitude is given by the formula where ES is the amplitude of therise or step of voltage, EP is the pulse amplitude and EK is the voltageacross condenser Cs at the time of the pulse EP. On the negative fallingedge (trailing edge, for example) of the pulse supplied to condenser C3by the pulse generator, diode Di will conduct and discharge condenserC3, but diode D2 will not conduct, thus leaving unchanged the voltage oncondenser Cd acquired during the immediately preceding positive rise ofthe pulse. The voltage on condenser C3 will be completely discharged toground through diode DI during this negative drop, or putting it inother words, the negative going edge of the pulses from the pulseoscillator is shorted to ground through diode Di. During the nextpositive rise in voltage caused by the succeeding pulse applied tocondenser C3, the condenser C3 will be recharged through diode D2. Itwill thus be seen that each time there is a positive rise in voltageapplied to condenser C3 by the pulse generator, there will be anincremental increase or step-up in voltage on condenser C4 although eachcharge on condenser C-l after the rst is slightly less than thepreceding one, due to the fact that EK, in the formula C3 ES= (EP-EK)mincreases with each step in the stair, and since the kc. pulse inputremains constant, ES in the above formula must decrease with each stepin the stair. At this time it should be noted that there is noresistance whatever across condenser C4, in order to avoid any currentor leakage charge during the voltage step-up operation.

Assuming that the voltage of the pulse applied by the 90 kc. pulseoscillator to condenser C3 has an amplitude of 400 volts, and takinginto account the previous assumption that the ratio of condenser C3 toC13 is 1 z2, the voltage on condenser Cll will be increased by about 20volts on the first step, and slightly less than 20 volts for the nextstep or rise. As mentioned before, each succeeding step or incrementalincrease in voltage on condenser C4 will be less than the preceding one.When the step Wave across condenser Cd reaches the cut-olf potential ofnormally non-conducting tube V, anode current will flow in tube V4through transformer T2, causing the tripping oscillator consisting ofvacuum tube V5 and transformer T2 to fire. The cut-off potential ofvacuum tube Vs is controlled by the values of resistor R5 and R5.

If the circuit elements associated with vacuum tube V4 are so designedthat the bias on the cathode of vacuum tube Vd is +165 volts, which wasan actual case in one application of the system of the invention to apulse type multiplex system, it will be evident that the voltage acrossC4 must exceed approximately +155 volts before tube V conducts. Thebuilding up of a charge on condenser C on the 9th rise to about voltswill cause tube V4 to start conducting very suddenly, as a result ofwhich a pulse of current is passed through transformer T2, whosewindings are so poled that it applies a sharp positive pulse to the gridof tube V5, thus causing tube V5 to conduct suddenly. The suddenconduction or firing of the tripping oscillator comprising vacuum tubeV5 causes a sharp positive pulse to be applied to the grid of normallynonconducting tube V3 over lead I3, thus causing tube V3 to conduct anddischarge the condenser C4 through this tube. It shouldbe noted at thistime that vacuum tube V5 is an overbiased pulse oscillator and isconnected regeneratively to produce only one pulse in response to theflow of current in tube Vd, after which the tube V5 ceases conducting.The triggering or ring of tube V produces a constant amplitude dischargepulse irrespective of the amplitude of the pulse from tube V4 and thisdischarge pulse produced by tube V5 is utilized to cause tube V3 toconduct suddenly. When tube V3 conducts, it produces a low impedancepath across the tube for the charge on condenser C4, and hence thiscondenser discharges through tube V3 to a relatively low value.

For the foregoing assumption and values of circuit elements, 'the timeconstants of the step generator or counter have been so designed thatthere are nine rises or incremental steps in voltage on condenser C4before this condenser is discharged. The wave form of the `step wavevoltage is shown in Fig. 2b and is taken from output lead I6. Each timethe tripping oscillator V5 res, there is produced a pulse whose Waveform is shown by curve Fig. 2c and taken from output lead I1. The pulsesof Fig. 2c occur at a frequency which is one-ninth of the frequency ofthe applied input waves to the counter. The duration of the pulses ofFig. 2c constituting the discharge pulse generated by trippingoscillator V5 and T2 is adjustable by means of resistor RT which is avariable resistor in the grid circuit of tube V5. When R1 is large, thetime required for tube V5 to charge condenser C1 is increased, resultingin tube V5 conducting for a longer period of time and hence resulting ina long output pulse for lead I7. The cycle of operation repeats itselfevery nine pulses of voltage applied to the counter by the 90 kc. pulseoscillator.

In order to change the number of steps in the step Wave voltageobtainable from lead I6, and hence the submultiple frequency derivedfrom lead Il, the amplitude of each step in the step wave voltage waveform must be changed. From the above mentioned equation,

it will be seen that the amplitude of each step can be varied by varyingthe pulse amplitude EP derived from the 90 kc. oscillator. This may bedone by varying the tap on resistor R2. The number of steps in the stepwave voltage can also be changed by changing the cut-01T potential valueof vacuum tube V4, and this is achieved by changing the values ofresistors R5 and R5. This last method of changing the number of steps inthe step wave voltage would, however, change the amplitude of thecomplete step Wave. If it is not desired to change the amplitude of thecomn plete step wave voltage, then the number of steps can be changed bychanging the amplitude of the output pulse from the 90 kc. pulseoscillator by adjusting resistor R2. When resistor R2 is at the minimumvalue with the screen grid tap nearest resistor R9, the count or numberof steps is the highest. When resistor R2 is at the maximum value withthe screen grid tap nearest resistor R80, the count or number of stepsis at the lowest value. This last result can also be achieved by varyingthe ratio of condenser C3 to condenser C4. Either one of thesecondensers can be made to be adjustable, preferably condenser C3, asshown, because it is smaller in size than condenser C. An adjustment ofresistor R2 or con-Y denser C3 in order to change the count will notappreciably change the overall step wave amplitude, although suchadjustment does change the amplitude of the individual steps or risers.

An advantageous feature inherent in the counter circuit is the snap-inaction, whereby the counter immediately jumps to its most favorableoperating conditionupon the adjustment of resistor R2 or condenser C3.As resistor R2 is adjusted to bring the count to the desired number(corresponding to the number of steps in the step Wave) the countabruptly changes. If resistor R2 is now adjusted in the oppositedirection, the count will not change at the same setting as it didpreviously, i. e., at the same resistance value of R2. This action isdue to the bias voltage developed across resistor R4 which is a functionof the frequency of the tripping oscillator V5, T2. Stated in otherwords, as the frequency of the tripping oscillator V5, T2 is changed dueto changing count, the average current in tubes V3 and V5 is changed,resulting in a change of voltage across resistor R4. When tube V3 ismade to conduct, it discharges the step condenser C4 to a value slightlyhigher than the voltage across R4. Hence, if the value of the voltagelacross R4 changes, then the value to which the step is discharged alsochanges, resulting in the counter circuit locking firmly at the positionfor bestoperation. For example, if the count is changed to a highernumber requiring a longer time interval for the step Wave voltage (Fig.2b), the voltage across resistor R4 drops when the counter abruptlychanges to the desired count. It should be understood that when thecount changes to a higher number, the number of step risers is increasedbut the amplitude of each step riser is decreased, thus requiring alonger time interval for the new step Wave voltage to reach the samecritical value at which the tube Vil conducts, as a result of which thefrequency of pulses from tripping oscillator V5, T2 is decreased to anew submultiple relation of the applied input pulses to the counter.When the pulse frequency of V5, T2 is thus decreased, the averagecurrent in V3 and V5 is decreased, resulting in a decreased voltagedeveloping across R4. Since the conducting point of tube V4 is fixed andthe amplitude of step wave voltage is also xed, it will be seen that byreducing the voltage across R4 to a desired value, the conduction pointof tube V4 on the new step wave voltage wave form can be made to takeplace at the middle of the new or added riser and this is a desiredoperating condition which is accomplishedY byproperly proportioning thevalues'of resistors R3 and R4 once and for all for all counts. In otherwords, the proper selection of resistors R3 and R4 holds true for allcounts over a desired range. With this adjustment, there is avoided thepossibility of unstable operation of the counter due to tolerablevariations in power supply voltages (for example, anode or lamentvoltages). It will be seen then, that the proper operating point at themiddle of a riser is automatically reached the instant the count ischanged from a lower to a higher number, and this feature is hereinreferred to as the snap-in action.

The snap-in feature has proved to be very useful because when resistorR2 is set to the transiion point as its resistance is increased, thecounter immediately jumps to the condition for most favorable operation,and further adjustment is unnecessary. Therefore, in order to assurethat the conducting point of tube V5.1 on the riser in the step wave isthe same for each adjustment of resistor R2, resulting in a chang@ incount, it is desirable to first adjust resistor R2 to give a lower countthan that desired and then vary R2 upwards (move the tap on R2 towardresistor Riti) until the desired count is reached.

The term "ground used in the specification and appended claims is notlimited to an earthed connection and is deemed to include any point ofzero potential for D. C. and alternating current.

What is claimed is:

1. A counter circuit comprising a rst condenser, a pair of rectierstructures each having a cathode and an anode, a direct connection fromsaid condenser to the anode of one rectier structure and the cathode ofthe other rectier structure, a second condenser connected between thecathode of said one structure and ground, a direct connection from theanode of said other structure to ground, rst, second and third triodevacuum tubes normally biased to cut-oit, direct current connections fromthe anode and cathode of said first tube to opposite sides of saidsecond condenser, whereby said first tube forms a discharge circuit forsaid second condenser. a connection from said second condenser to thegrid of said second tube, whereby said second tube becomes conductivewhen the charge on said second condenser overcomes the cut-off value onsaid second tube, a direct connection between the cathodes of said firstand third tubes, a direct connection between the anodes of said secondand third tubes, a transformer having one winding connected between asource of anode polarizing potential and the anode of said third tube,and having another winding regeneratively coupled to the grid of saidthird tube, whereby said third tube and said transformer comprise atripping oscillator, and a connection from said tripping oscillator tothe grid of said first tube to supply to said last grid a voltage pulseof positive polarity of sufficient magnitude toy cause said first tubeto conduct and thereby discharge said` second condenser whenever saidtripping oscillator is red.

2.v A counter circuit comprising a` iirst condenser, a pair of rectifierstructures each having a cathode and an anode, al direct connection fromsaid condenser to the anode of one rectifier structure and the cathodeof the other rectifier structure, a second condenser connected betweenthe cathode of said one structure and ground, a direct connection fromthe anode of said other structure to ground, first, second and thirdtriode vacuum tubes normally biased to cut-01T, a direct connection fromthe anode of the first tube to the cathode of said one structure, aresistor shunted by a by-pass condenser connected between ground and thecathode of said rst tube, whereby said first tube forms a dischargecircuit for said second condenser, a connection from said secondcondenser to the grid of said r second tube, whereby said second tubebecomes conductive when the charge on said second condenser overcomesthe cut-oii7 value of said second tube, a direct connection between thecathodes of said first and third tubes, a direct connection between theanodes of said second and third tubes, a transformer having one windingconnected between a source of anode polarizing potential and the anodeof said third tube, and having another winding regeneratively coupled tothe grid of said third tube, whereby said third tube and saidtransformer comprise a tripping oscillator, and a connection from saidtripping oscillator to the grid of said first tube to supply to saidlast grid a voltage pulse of positive polarity of sufficient magnitudeto cause said tube to conduct and thereby discharge said secondcondenser whenever said tripping oscillator is fired.

3. A counter circuit comprising a rst condenser, a pair of rectifierstructures each having a cathode and an anode, a direct connection fromsaid condenser to the anode of one rectifier structure and the cathodeof the other rectier structure, a second condenser connected between the8 cathode of said one structure and ground, a direct connection from theanode of said other structure to ground, first, second and third triodevacuum tubes normally biased to cut-off,- a direct connection from theanode of the first tube to the cathode of said one structure, a resistorshunted by a bypass condenser connected between ground and the cathodeof said nrst tube, whereby said rst tube forms a discharge circuit forsaid second condenser, a resistor connecting the cathode of said firsttube to a source of positive potential, a connection from said secondcondenser to the grid of said second tube, whereby said second tubebecomes conductive when the charge on said second condenser overcomesthe cut-off value on said second tube, a direct connection between thecathodes of said rst and third tubes, a direct connection between theanodes of said second and third tubes, a transformer having one windingconnected between a source of anode polarizing potential and the anodeof said third tube, and having another winding regeneratively coupled tothe grid of said third tube, whereby said third tube and saidtransformer comprise a tripping oscillator, and a connection from saidtripping oscillator to the grid of said first tube to supply to saidlast grid a voltage pulse off positive polarity of sucient magnitude tocause said rst tube to conduct and thereby discharge said secondcondenser whenever said tripping oscillator is fired.-

4. A counter circuit comprising a iirst condenser, a pair of rectiiierstructures each having an anode and a cathode, a direct connection fromsaid condenser to the anode of one rectifier structure and the cathodeof the other rectiiier structure, a second condenser connected betweenthe cathode of said one' structure and ground, a direct connection fromthe anode oi said other structure to ground, an electric' tube' havingan anode connected over a direct current path to one side of said secondcondenser and a cathode connected through a resistor to the other sideof said second condenser, a resistor connected between said cathode andthe positive terminal or" a source of unidirectional potential, and anelectron discharge device circuit responsive to a predeterminedmagnitude of charge on said second icondenser for rendering' saidelectric tube conductive to thereby discharge said second condenser,means for applying recurring waves to said rst condenser-,whereby anincremental increase in voltage i's developed across said secondcondenser for each input recurringwave during a cycle of operation ofsaid counter, said means including an adjustable resistor arrangementfor changing the amplitude of said recurring waves, and an outputcircuit coupled to said second condenser for deriving' therefrom astep-Wave voltage.

5. A counter circuit comprising a iirst condenser, a pair of rectifierstructures each having a cathode and an anode, a direct connection fromSaid condenser to the anode of one rectifier structure andthe cathode ofthe other rectier structure, a second condenser connected between theanode of said one. structure and ground, a direct connection from theanode ofsaid other structure to ground, first, second and third triodevacuumtubes normally biased to cut-off, a direct current connection fromthe anode of said iirst tube to one side of said secondy condenser, aconne'ctionv including a series resistor from the cathode ofY saidfirsttub-e to the otherside of said second condenser, whereby said first tubeforms a discharge circuit for said secondV condenser,

another resistor connected between said cathode and the positiveterminal of a source of unidirectional potential, a connection from saidsecond condenser to the grid of said second tube, whereby said secondtube becomes conductive when the charge on said second condenserovercomes the cut-01T value on said second tube, a direct connectionbetween the cathodes of Said rst and third tubes, a direct connectionbetween the anodes of said second and third tubes, a transformer havingone winding connected between a source of anode. polarizing potentialand the anode of said third tube, and having another windingregeneratively coupled to the grid of said third tube, whereby saidthird tube and said transformer comprise a tripping oscillator, and aconnection from said tripping oscillator to the grid of said first tubeto supply to said last grid a voltage pulse of positive polarity ofsuicient magnitude to cause said rst tube to conduct and therebydischarge said second condenser-whenever said tripping oscillator isxed.

6. A counter circuit comprising a first condenser, a pair of rectierstructures each having an anode and a cathode, a direct connection fromsaid condenser to the anode of one rectifier structure and the cathodeof the other rectifier structure, a second condenser connected betweenthe cathode of said one structure and ground, a direct connection fromthe anode of said other structure to ground, an electric tube having ananode connected over a direct current path to one side of said secondcondenser and a cathode connected through a resistor to the other sideof said second condenser, a resistor connected between said cathode andthe positive terminal of a source of unidirectional potential, and anelectron discharge device circuit responsive to a predeterminedmagnitude of charge on said second condenser for rendering said electrictube conductive to thereby discharge said second condenser, means forapplying adjustable amplitude recur ring waves to said rst condenser,whereby an incremental increase in voltage is developed across saidsecond condenser for each input recurring wave during a cycle ofoperation of said counter, said means including an adjustable resistorarrangement for changing the amplitude of said recurring waves, and anoutput circuit coupled to said second condenser for deriving therefrom astep-wave voltage.

WILLIAM D. HOUGHTON.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,113,011 White Apr. 5, 19332,411,573 Holst Nov. 26, 1946 2,413,440 Farrington Dec. 31, 19462,416,188 McClellan Feb. 18, 1947

